The present technique relates to servo control device and optical disc device including a differential phase detection (DPD) circuit for detection of a tracking error (TE) signal for example.
In the optical disc controller large-scale integration (LSI), equipping of the DPD circuit is indispensable for tracking error (TE) signal detection in a read only memory (ROM) disc such as Blu-ray disc (BD) and digital versatile disc (DVD).
Although the DPD circuit is based on a full-analog configuration in the past, digital DPD is coming to be employed in recent years for circuit scale reduction and power consumption suppression in a high-density process (refer to e.g. Japanese Patent Laid-opens No. 2006-260645, No. 2001-67690, and No. 2009-9660).
In the servo system employing the digital DPD, the sampling frequency (fs) of analog/digital (A/D) conversion for DPD needs to be a fixed frequency synchronized with the servo system clock because servo control is carried out by a servo digital signal processor (DSP).
Furthermore, because of the sampling theorem, the sampling frequency fs needs to be kept at least twice the radio frequency (RF) maximum repetition frequency (repeated minimum toggle runlength (rmtr)).